hardening 4130

[gibsoni]

Hi,

Can someone inform me on how hard I can make 4130 bar?

How is this achieved best? I need to harden the end of a 3/16" rod so that repeated striking on the head of a nail does not deform it. Should I be using a different material like 4140?

Regards, Iain.

 

[metman]

4140 will give you higher hardness. It can be oil quenched after heating the end to cherry red. The same thing can be done with 4130 but the hardness will be lower.

4130 is 0.3% Carbon
4140 is 0.4% Carbon

The higher the Carbon, the higher the hardness.

4140 as quenched will give you about 60 HRC hardness.

After quenching, temper at 500 degrees F for 30 minutes. This will reduce the hardness but will provide some toughness for hammering.

 

[salmon2]

I second 4140 as metman input because of higher hardness and it's puopularity unless invovels welding. Of course 4142 and 4145 will be just fine as well.

 

[gibsoni]

Thanks for the replies.

I cannot yet find a supplier of small (approx 5mm) round bar in 4140, but can in 4130, hence my question.

How hard can 4130 be made?

Regards, Iain.

 

[metman]

4130 will harden to HRC 51 by water quenching. After tempering at 500 the hardness will be less.

You can carburize 4130 for higher surface hardness up to 65 HRC if you have enough pieces to justify the cost of a furnace run.

If you have only one piece, you can use Kasenite to surface harden with an oxy-acetelyne torch.

 

[salmon2]

Gibsoni, in the below file, page 12-13, you can find the hardness/strength range depending on tempering temperature:

http://www.emjmetals.com/pdf/bluebook-r.pdf

Be aware of the tempering embrittlement range: 500F~800F, which results in lower Izod impact toughness.

I found this info from one of my previous posts as below, where tbuelna told me about EMJ website, excellent website.

http://eng-tips.com/viewthread.cfm?qid=284981&page=2

 

[metman]

Gibsoni did what I hoped someone would do. He gave you a link for hardness vs tempering temperature. And his advice about the embrittlement range is why I recommended 500F tempering.

I need to revise my comment above. HRC 51 is for 1/2" round whereas 3/16" will quench faster and therefore could be as hard as 55 HRC. And now that you have the tempering chart, you can select a tempering temperature (maybe 500F) that will give you about 50 HRC. If you go over 55, it will be brittle and chip with impact loading. However, 4130 will not harden more than 55 HRC so even a 400F tempering temperature should be adequate to eliminate brittleness associated with untempered Martensite.